Selenium copper compound and preparation method and application thereof

Abstract

The invention discloses a selenium copper compound as well as a preparation method and application thereof. The preparation process of the selenium copper compound comprises the following steps: dissolving selenium powder in an alkaline solution under a heating condition, then adding a reducing agent, then carrying out a co-precipitation reaction with a mixed solution containing copper salt and a surfactant, and filtering, washing and drying a reaction product to obtain the selenium copper compound, or dissolving raw materials including copper salt in an alkaline solution, then adding a reducing agent to carry out precipitation reaction, filtering, washing and drying a reaction product to obtain orange red powder, and co-roasting the orange red powder and selenium powder to obtain the selenium-rich copper oxide. Compared with a common chalcogenide, the selenium copper compound has higher conductivity, also has multiple crystal structures, and endows the material with higher electrocatalytic activity and stability. Tests show that the energy efficiency of the flow battery adopting the selenium-copper compound modified negative electrode can reach about 80% under the current density of 80mA / cm < 2 >, and the energy storage performance of the flow battery is greatly improved.

Description

Technical Field

[0001] The present invention relates to a selenium copper compound, specifically to a selenium copper compound, a preparation method thereof and an application thereof, belonging to the technical field of flow batteries. Background Art

[0002] Redox flow batteries are a very promising energy storage technology due to their high safety, long cycle life, and independent power and energy. They can solve the problems of instability and uncontrollability brought by discontinuous renewable energy sources such as wind energy and solar energy. Among various flow batteries, flow batteries with polysulfides as redox couples are gradually coming into the public eye due to their low cost and easily available raw materials. However, the low redox activity of polysulfides themselves and the slow reaction kinetics result in poor efficiency of flow batteries based on polysulfide couples, hindering their commercial development.

[0003] At present, most of the electrodes used in flow batteries are carbon electrodes, which have the advantages of good conductivity and high specific surface area. However, the activity of unmodified carbon electrodes is limited. Therefore, it is necessary to seek electrodes with higher activity to meet the requirements. Foam metal electrodes represented by nickel foam have higher catalytic activity. However, since the metal will react with polysulfide ions in the electrolyte to form metal sulfides, and the metal sulfides do not have a dense structure and cannot prevent their continuous reaction with polysulfides, the battery performance cannot be effectively improved. Therefore, there is an urgent need in the market for a material with high catalytic activity to enhance the redox activity of polysulfides and improve the overall performance of flow batteries. Summary of the Invention

[0004] Aiming at the problems existing in the prior art, the first object of the present invention is to provide a selenium copper compound. The direct band gap of the selenium copper compound provided by the present invention is between 2.1 and 2.39 eV, and the indirect band gap is between 1.2 and 1.7 eV, which has higher conductivity compared with general chalcogenide compounds. In addition, the selenium copper compound also has a variety of crystal structures, endowing the material with higher electrocatalytic activity and stability.

[0005] The second object of the present invention is to provide a preparation method of a selenium copper compound. The preparation method directly reacts a copper salt with selenium powder by a liquid-phase co-precipitation method or a programmed temperature solid-phase sintering method to obtain a polycrystalline selenium copper compound. In particular, the liquid-phase co-precipitation method can directly synthesize nano-scale selenium copper compounds under low-temperature conditions, and the morphology of the obtained selenium copper compounds can be directly regulated by controlling the types and amounts of reducing agents and surfactants.

[0006] The third object of the present invention is to provide an application of a selenium copper compound for modifying the negative electrode of a polysulfide flow battery. Based on the unique properties and structure of the above selenium copper compound, using it to modify the negative electrode of a polysulfide flow battery has excellent technical effects. After testing, the flow battery using the above selenium copper compound modified negative electrode can reach an energy efficiency of about 80% under a current density of 80 mA / cm 2 and greatly improve the energy storage performance of the flow battery.

[0007] To achieve the above technical object, the present invention provides a preparation method of a selenium copper compound, including: dissolving selenium powder in an alkaline solution under heating conditions to obtain a clear solution A; adding a reducing agent to the clear solution A to obtain a solution B; dissolving a copper salt and a surfactant in deionized water to obtain a solution C; adding the solution B to the solution C for a coprecipitation reaction, and filtering, washing and drying the reaction product to obtain it;

[0008] Or, dissolving raw materials including a copper salt in an alkaline solution, adding a reducing agent for a precipitation reaction, filtering, washing and drying the reaction product to obtain an orange-red powder, and co-roasting it with selenium powder to obtain it;

[0009] The mass ratio of the selenium powder, the reducing agent and the copper salt is 1:(1-2):(1-2).

[0010] In the method provided by the present invention, by strictly controlling the addition amounts between the main raw materials, while achieving the efficient synthesis of the selenium copper compound, the crystal morphology of the selenium copper compound is effectively controlled and its dispersibility is improved, and the product agglomeration is greatly reduced; it should be noted that if the addition amount of the reducing agent is too high, there will be excessive SeO3 in the solution 2- , if the addition amount of the reducing agent is too low, it is not enough to reduce the selenium powder to Se 2- , which will affect the purity and yield of the final product.

[0011] As a preferred scheme, when the molar ratio of selenium element to copper element of the selenium powder and the copper salt is 1:0.8-1, the main component of the obtained selenium copper compound is CuSe.

[0012] As a preferred scheme, when the molar ratio of selenium element to copper element of the selenium powder and the copper salt is 1:1.8-2, the main component of the obtained selenium copper compound is Cu3Se2.

[0013] As a preferred scheme, the alkaline solution is at least one of sodium hydroxide, potassium hydroxide and sodium sulfite solution.

[0014] As a preferred solution, the reducing agent is at least one of cystine, cysteine, glutathione and ascorbic acid. The organic reducing agents listed in the present invention have similar reducing abilities, require mild reaction conditions, and can act as both reducing agents and surface modifiers during the reaction, thereby further regulating the crystal morphology.

[0015] As a preferred solution, the copper salt is a soluble divalent copper salt. Further preferably, the copper salt is copper sulfate.

[0016] As a preferred solution, the surfactant is any one of polyvinyl alcohol, polyvinyl pyrrolidone, polyacrylic acid and polyethylene glycol. The surfactant can selectively interact with different crystal faces to change their surface energy. By adding an appropriate amount of surfactant, the size and crystal structure of the product can be regulated.

[0017] As a preferred solution, the added amount of the surfactant does not exceed 10wt% of the mass of the copper salt.

[0018] As a preferred solution, the mass ratio of the orange-red powder to the selenium powder is 1:(1-2).

[0019] As a preferred solution, the co-sintering conditions are: in a protective atmosphere, the temperature is raised from room temperature to 300-400°C at 8-12°C / min, kept at this temperature for 2-5 hours, and then cooled to room temperature with the furnace. Too high a temperature will lead to too fast a grain growth rate, too large a crystal size, and easy agglomeration, while too low a temperature will not reach the transformation temperature of CuSe to CuSe2.

[0020] The present invention also provides a copper selenide obtained by any one of the preparation methods described above; the copper selenide is Cu x Se y ; Among them, the value range of x:y is (1~3):2.

[0021] The present invention also provides an application of copper selenide for modifying the negative electrode of a polysulfide flow battery, and the process is as follows: the copper selenide and Nafion resin are dissolved in ethanol and fully mixed to obtain a modified slurry, which is then evenly coated on the surface of the negative electrode of the flow battery and dried.

[0022] The present invention uses copper selenide as a surface modifier for the negative electrode of a liquid flow battery, which not only greatly improves the conductivity and electrocatalytic activity of the electrode, but also, based on its excellent stability, avoids its reaction with polysulfide ions in the electrolyte of the liquid flow battery, thereby completely solving the problem in the prior art that metal-modified electrodes are prone to react with polysulfide ions to form metal sulfides, resulting in low battery efficiency, and greatly improves the comprehensive performance of liquid flow batteries, especially polysulfide liquid flow batteries.

[0023] As a preferred embodiment, the mass ratio of the copper selenide to the Nafion resin is (1.5~15):1. The Nafion resin serves as a binder to bond the copper selenide to the carbon felt, preventing it from falling off easily during cycling and ensuring the stability of the electrode. Further, the Nafion resin is also an ion-exchange resin, which can play a role in ion / electron conduction, helping to reduce the negative impact of the binder on the electrode conductivity. The addition amount of the Nafion resin must be strictly in accordance with the above requirements. Too little resin will result in weak bonding and easy falling off, while too much will affect the contact between the catalyst and the active substance, leading to an increase in internal resistance and affecting the electrode performance.

[0024] As a preferred embodiment, the drying process is as follows: drying the material in an oven at 50~80°C until constant weight.

[0025] As a preferred embodiment, the polysulfide flow battery includes: a positive electrode, a negative electrode coated with copper selenide, a positive electrolyte, a negative electrolyte, and an ion-exchange membrane.

[0026] As a preferred embodiment, the positive electrode is a carbon felt, and the negative electrode is a carbon felt coated with copper selenide.

[0027] As a preferred embodiment, the positive electrolyte is a potassium ferricyanide alkaline solution.

[0028] As a preferred embodiment, the negative electrolyte is a sodium disulfide alkaline solution.

[0029] As a preferred embodiment, the ion-exchange membrane is a Nafion membrane. Further preferably, the ion-exchange membrane is a Nafion 212 membrane.

[0030] Compared with the prior art, the beneficial technical effects of the technical solution of the present invention are as follows:

[0031] 1) The direct bandgap of the copper selenide provided by the present invention is between 2.1~2.39 eV, and the indirect bandgap is between 1.2~1.7 eV. It has higher conductivity compared with general chalcogenide compounds. In addition, the copper selenide also has a variety of crystal structures, endowing the material with higher electrocatalytic activity and stability.

[0032] 2) The preparation method provided by the present invention uses the liquid-phase co-precipitation method or the programmed temperature solid-phase sintering method to directly react copper salts with selenium powder to obtain polycrystalline copper selenide. Especially, the liquid-phase co-precipitation method can directly synthesize nano-scale copper selenide under low-temperature conditions, and the morphology of the obtained copper selenide can be directly regulated by controlling the types and amounts of reducing agents and surfactants. In addition, this method also has the advantages of low synthesis difficulty, simple operation, easy control, and suitability for large-scale production.

[0033] 3) In the technical solution provided by the present invention, based on the unique properties and structure of the above-mentioned selenium copper compound, using it to modify the negative electrode of the polysulfide flow battery has excellent technical effects. After testing, the flow battery using the above-mentioned selenium copper compound to modify the negative electrode can achieve an energy efficiency of about 80% at a current density of 80 mA / cm 2 , greatly improving the energy storage performance of the flow battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 XRD image of CuSe provided in Example 1 of the present invention;

[0035] Figure 2 Cyclic voltammogram of CuSe provided in Example 1 of the present invention in a polysulfide ion solution;

[0036] Figure 3 Rate performance diagram of a lithium-sulfur battery using a CuSe-modified negative electrode;

[0037] Figure 4 XRD image of Cu3Se2 provided in Example 2 of the present invention;

[0038] Figure 5 Cyclic voltammogram of Cu3Se2 provided in Example 2 of the present invention in a polysulfide ion solution; Figure 6 Rate performance diagram of a lithium-sulfur battery using a Cu3Se2-modified negative electrode;

[0039] Figure 7 XRD image of CuSe2 provided in Example 3 of the present invention;

[0040] Figure 8 Cyclic voltammogram of CuSe2 provided in Example 3 of the present invention in a polysulfide ion solution;

[0041] Figure 9 Rate performance diagram of a lithium-sulfur battery using a CuSe2-modified negative electrode;

[0042] Figure 10 Rate performance diagram of a lithium-iodine battery using a CuSe-modified negative electrode provided in Example 1 of the present invention;

[0043] Figure 11 Rate performance diagram of the lithium-sulfur battery provided in Comparative Example 1 of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0044] The technical solutions of the present invention will be further described in detail below in conjunction with specific embodiments and drawings. To facilitate the understanding of the present invention, the present invention will be described more comprehensively and meticulously below in conjunction with the specification drawings and preferred embodiments. It should be noted that the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the scope of protection of the present invention.

[0045] In the embodiments of the present invention, those not specified under specific conditions are carried out according to conventional conditions or conditions recommended by the manufacturer. Reagents or instruments not specified for the manufacturer are all conventional products that can be obtained by conventional technical means or purchased through the market.

[0046] Example 1

[0047] This example provides a selenium copper compound, and its specific preparation process is as follows:

[0048] 0.05 mol of selenium powder and 0.3 mol of sodium hydroxide are added to 80 ml of deionized water, and stirred for 0.5 h to form a homogeneous solution; cysteine (the ratio of cysteine to selenium powder is 4:3) is added to the solution, heated to 80 °C, and stirred for another 0.5 h to obtain a homogeneous solution; 0.045 mol of copper sulfate and 1 g of polyvinylpyrrolidone are added to 100 ml of deionized water, and stirred for 0.5 h to form a homogeneous transparent solution; the two solutions are mixed and stirred for 1.5 h. After the reaction is completed, the obtained mixed solution is filtered, washed three times with deionized water and ethanol respectively, and then the obtained solid is dried at 60 °C for 12 h to obtain the product.

[0049] The XRD pattern of the selenium copper compound obtained in this example is as Figure 1 shown, and its crystal form is hexagonal crystal form, and the main component is CuSe.

[0050] To more intuitively reflect the advantages of the technical solutions of the present invention, the present invention also carried out electrochemical performance tests on the above selenium copper compound. Specifically: the prepared selenium copper compound powder catalyst is added to ethanol, 50 μl of Nafion resin is added as a binder, and ultrasonicated for 1 h to obtain a homogeneous slurry ink, wherein the content of the selenium copper compound is 18 mg / ml. In this example, the three-electrode system is used for the electrochemical performance test. The working electrode is a glassy carbon electrode loaded with the catalyst, and the loading amount is 0.9 mg / cm 2 , the counter electrode is a platinum mesh of 1×1.5 cm 2 , the reference electrode is a Hg / HgO electrode, the electrolyte is 0.1 mol / L of Na2S2 + 1 mol / L of NaOH, the scanning rate is 10 mv / s, and argon gas is continuously introduced during the test to prevent the electrolyte from being oxidized.

[0051] like Figure 2 As shown in the figure, the blank glassy carbon electrode has no oxidation peak and reduction peak, indicating that pure glassy carbon has no redox activity, while the glassy carbon electrode loaded with the above-mentioned copper selenide has three obvious reduction peaks, corresponding to S4 2- 、S2 2- , S 2- The peak currents of the reduction peak, oxidation peak and reduction peak also increased further, indicating that copper selenide has obvious catalytic activity for the redox reaction of polysulfide ions.

[0052] Furthermore, the present invention also uses the above-mentioned copper selenide to modify the negative electrode of the sulfur-iron battery, specifically: the above-mentioned copper selenide and Nafion resin are added to ethanol and mixed evenly to obtain a uniform slurry, and then evenly loaded on the carbon felt, and dried at 60°C for use. The battery uses unloaded carbon felt as the positive electrode and the copper selenide modified electrode as the negative electrode; the positive electrode electrolyte is 0.3M K3Fe(CN)6+1M NaOH, and the negative electrode electrolyte is 0.5M Na2S2+1M NaOH; the volume of the positive and negative electrolytes is 70ml; the ion exchange membrane is Nafion212; a polysulfide-based sulfur-iron liquid flow battery is assembled, and the rate test range is 20-140mA / cm 2 , the current density interval is 20mA / cm 2 .

[0053] like Figure 3 As shown, the performance of the electrode battery modified with the selenium copper compound prepared in this example is very excellent, at 20 mA / cm 2 Under high current density, its energy efficiency is as high as 91%, and the current density increases to 120 mA / cm 2 When the energy efficiency is 69%, it can still reach 69%. It can be seen that the performance of the electrode modified by copper selenide catalyst is higher than that of the commercial original carbon felt electrode, and can be widely used in polysulfide system liquid flow batteries.

[0054] Example 2

[0055] This embodiment provides a copper selenide, and the specific preparation process is as follows:

[0056] Add 4mmol selenium powder and 10mmol sodium sulfite to 50ml deionized water, heat to 80℃ and stir for 2h; cool the reacted solution to room temperature and filter to obtain supernatant; add 8mmol copper sulfate to the supernatant and stir for 2h; after the reaction, filter the mixed solution, wash it three times with deionized water and ethanol, and dry the solid at 60℃ for 12h.

[0057] The XRD spectrum of the copper selenide obtained in this example is as follows Figure 4As shown, its crystal form is tetragonal and its main component is Cu3Se2.

[0058] In order to more intuitively reflect the advantages of the technical solution of the present invention, the present invention also conducted an electrochemical performance test on the above-mentioned copper selenide, specifically: the prepared copper selenide powder was added to ethanol, 50ul of Nafion resin was added as a binder, and ultrasonicated for 1h to obtain a uniform slurry ink, wherein the content of copper selenide was 6mg / ml. In this embodiment, the electrochemical performance test adopted a three-electrode system, the working electrode was a glassy carbon electrode loaded with catalyst, and the loading amount was 0.3mg / cm 2 , the counter electrode is 1×1.5cm 2 The reference electrode was a Hg / HgO electrode, the electrolyte was 0.1 mol / L Na2S2 + 1 mol / L NaOH, the scanning rate was 10 mv / s, and argon was continuously introduced during the test to prevent the electrolyte from being oxidized.

[0059] like Figure 5 As shown in the figure, the blank glassy carbon electrode has no oxidation peak and reduction peak, indicating that pure glassy carbon has no redox activity, while the glassy carbon electrode loaded with the above-mentioned copper selenide has three obvious reduction peaks, corresponding to S4 2- 、S2 2- , S 2- The peak currents of the reduction peak, oxidation peak and reduction peak also increased further, indicating that the copper selenide has obvious catalytic activity for the redox reaction of polysulfide ions.

[0060] Furthermore, the present invention also uses the above-mentioned copper selenide to modify the negative electrode of the sulfur-iron battery, specifically: the prepared copper selenide and Nafion resin are added to ethanol and mixed evenly to obtain a uniform slurry, and then evenly loaded on the carbon felt, and dried at 60°C for use. The battery uses unloaded carbon felt as the positive electrode and a loaded copper selenide electrode as the negative electrode; the positive electrode electrolyte is 0.3M K3Fe(CN)6+1M NaOH, and the negative electrode electrolyte is 0.5M Na2S2+1M NaOH; the volume of the positive and negative electrolytes is 70ml; the ion exchange membrane is Nafion212; a polysulfide-based sulfur-iron liquid flow battery is assembled, and the rate test range is 20-140mA / cm 2 , the current density interval is 20mA / cm 2 .

[0061] from Figure 6 As shown, the battery performance of the electrode modified with selenium copper prepared in this example is very excellent, at 20 mA / cm 2 Under high current density, its energy efficiency is as high as 93%, and the current density increases to 120 mA / cm 2When the energy efficiency can still reach 64%. It can be seen that the Cu3Se2 catalyst has excellent catalytic activity for the polysulfide system and is also very suitable for the redox flow battery of the polysulfide system.

[0062] Example 3

[0063] This example provides a copper selenide, and its specific preparation process is as follows: Add 7.5 mmol of copper sulfate and 2.5 mmol of sodium citrate to 500 ml of sodium hydroxide solution, stir for 0.5 h to obtain a mixed solution; add 7.5 mmol of ascorbic acid to the above mixed solution and continue to react for 0.5 h; after the reaction, filter the obtained mixed solution, wash it 3 times with deionized water and ethanol respectively, and dry it at 60 °C for 12 h to obtain Cu2O powder; place Cu2O and selenium powder in a tube furnace according to a mass ratio of 1:2, and react at 300 °C for 3 h in an Ar atmosphere to obtain it.

[0064] The XRD pattern of the copper selenide obtained in this example is as Figure 7 shown, its crystal form is tetragonal crystal form, and the main component is CuSe2.

[0065] To more intuitively reflect the advantages of the technical solution of the present invention, the present invention also carried out electrochemical performance tests on the above copper selenide. Specifically: Add the prepared CuSe2 powder catalyst to ethanol, add 50 μl of Nafion resin as a binder, and ultrasonicate for 1 h to obtain a uniform slurry ink, wherein the content of the catalyst is 6 mg / ml. In this example, the three-electrode system is used for the electrochemical performance test. The working electrode is a glassy carbon electrode loaded with the catalyst, and the loading amount is 0.3 mg / cm 2 , the counter electrode is a platinum mesh of 1×1.5 cm 2 , the reference electrode is a Hg / HgO electrode, the electrolyte is 0.1 mol / L Na2S2 + 1 mol / L NaOH, the scanning rate is 10 mv / s, and argon gas is continuously introduced during the test to prevent the electrolyte from being oxidized.

[0066] As Figure 8 shown, there are three obvious reduction peaks on the glassy carbon electrode loaded with the above copper selenide, corresponding to the reduction peaks of S4 2- , S2 2- , S 2- from right to left respectively, and the peak currents of the oxidation peak and the reduction peak also increase further, indicating that the copper selenide has obvious catalytic activity for the redox reaction of polysulfide ions.

[0067] Furthermore, the present invention also uses the above-mentioned copper selenide to modify the negative electrode of the polysulfide iron battery. Specifically: the prepared copper selenide and Nafion resin are added to ethanol and mixed evenly to obtain a uniform slurry, which is then evenly loaded onto carbon felt and dried at 60 °C for use. The battery uses unloaded carbon felt as the positive electrode and the electrode loaded with copper selenide as the negative electrode; the positive electrolyte is 0.3 M K3Fe(CN)6 + 1 M NaOH, and the negative electrolyte is 0.5 M Na2S2 + 1 M NaOH; the volume of both the positive and negative electrolytes is 70 ml; the ion exchange membrane is Nafion212; a polysulfide-based polysulfide iron flow battery is assembled, and the rate test range is 20-140 mA / cm 2 , and the current density interval is 20 mA / cm 2 .

[0068] As shown in Figure 9 , the battery performance of the electrode modified with the copper selenide prepared in this example is excellent. At a current density of 20 mA / cm 2 , its energy efficiency is as high as 91%. When the current density increases to 100 mA / cm 2 , the energy efficiency can still reach 64%. It can be seen that the CuSe2 catalyst also has excellent catalytic activity for the polysulfide system and is also applicable to the redox flow battery of the polysulfide system.

[0069] Example 4

[0070] In this example, the electrode loaded with CuSe prepared in Example 1 above was applied to a sulfur-iodine flow battery. The specific process is as follows:

[0071] The battery uses unloaded carbon felt as the positive electrode and the electrode loaded with CuSe as the negative electrode; the positive electrolyte is 0.75 M NaI + 1 M NaOH, and the negative electrolyte is 0.5 M Na2S2 + 1 M NaOH; the volume of both the positive and negative electrolytes is 70 ml; the ion exchange membrane is Nafion212; a polysulfide-based sulfur-iodine flow battery is assembled, and the rate test range is 20-140 mA / cm 2 , and the current density interval is 20 mA / cm 2 , and its rate performance is as shown in Figure 10 .

[0072] As shown in Figure 10 , it can be seen that the battery performance of the electrode modified with the CuSe catalyst prepared in this example has been significantly improved. At the same current density of 20 mA / cm 2 , its energy efficiency is as high as 83%. When the current density increases to 100 mA / cm 2When the energy efficiency can still reach 59%. It can be seen that the electrode modified by copper selenide catalyst can be applied not only to the sulfur-iron battery, but also to other polysulfide-based redox flow batteries.

[0073] Comparative Example 1

[0074] The carbon felt without loading is used as the electrode for both the positive and negative electrodes of the battery; the positive electrolyte is 0.3M K3Fe(CN)6 + 1M NaOH, and the negative electrolyte is 0.5M Na2S2 + 1M NaOH; the volumes of both the positive and negative electrolytes are 70 ml; the ion exchange membrane is Nafion212; a polysulfide-based sulfur-iron redox flow battery is assembled, and the rate test range is 20 - 140 mA / cm 2 , and the current density interval is 20 mA / cm 2 , and its rate performance is as Figure 11 shown.

[0075] From Figure 11 it can be seen that the battery performance of the carbon felt electrode without catalyst modification is very poor, and it can only operate at low current density, and cannot continue to operate when the current density exceeds 40 mA / cm 2 .

Claims

1. A method for preparing a selenium copper compound, characterized in that, Comprising: Dissolving selenium powder in an alkaline solution under heating conditions to obtain a clear solution A; Adding a reducing agent to the clear solution A to obtain a solution B; Dissolving a copper salt and a surfactant in deionized water to obtain a solution C; Adding the solution B to the solution C for coprecipitation reaction, and subjecting the reaction product to filtration, washing and drying to obtain the product; Alternatively, dissolving raw materials including a copper salt in an alkaline solution, adding a reducing agent for precipitation reaction, subjecting the reaction product to filtration, washing and drying to obtain an orange-red powder, and co-roasting with selenium powder to obtain the product; The molar ratio of the selenium powder, the reducing agent and the copper salt is 1:(1 - 2):(1 - 2).

2. The preparation method of a selenium copper compound according to claim 1, characterized in that: The alkaline solution is at least one of sodium hydroxide, potassium hydroxide and sodium sulfite solution; the reducing agent is at least one of cystine, cysteine, glutathione and ascorbic acid.

3. The preparation method of a selenium copper compound according to claim 1, wherein: The copper salt is a soluble divalent copper salt; the surfactant is any one of polyvinyl alcohol, polyvinylpyrrolidone, polyacrylic acid and polyethylene glycol.

4. The preparation method of a selenium copper compound according to claim 1, wherein: The addition amount of the surfactant does not exceed 10 wt% of the mass of the copper salt; the mass ratio of the orange-red powder to the selenium powder is 1:(1 - 2).

5. The preparation method of a selenium copper compound according to claim 1, characterized in that: The conditions for the co-roasting are: under a protective atmosphere, heating from room temperature to 300 - 400 °C at 8 - 12 °C / min, holding for 2 - 5 h, and then cooling to room temperature with the furnace.

6. A selenium copper compound, characterized in that: Obtained by the preparation method according to any one of claims 1 to 5; the selenium copper compound is Cu x Se y ; wherein, the value range of x:y is (1 to 3):

2.

7. Use of the copper selenide according to claim 6, characterized in that: For modifying the negative electrode of a polysulfide flow battery, the process is: dissolving the above selenium copper compound and Nafion resin in ethanol and mixing well to obtain a modified slurry, and then uniformly coating it on the surface of the negative electrode of the flow battery and drying to obtain the product.

8. Use of the copper selenide according to claim 7, characterized in that: The mass ratio of the selenium copper compound to the Nafion resin is (1.5 - 15):1; the drying process is: drying the material in an oven at 50 - 80 °C to constant weight.

9. Use of the copper selenide according to claim 8, characterized in that: The polysulfide flow battery includes: a positive electrode, a negative electrode coated with a selenium copper compound, a positive electrode electrolyte, a negative electrode electrolyte and an ion exchange membrane.

10. The application of the copper selenide according to claim 9, characterized in that: The positive electrode is a carbon felt, the negative electrode is a carbon felt coated with a selenium copper compound; the positive electrode electrolyte is any one of ferricyanide alkali solution and polyiodide alkali solution; the negative electrode electrolyte is sodium disulfide alkali solution; the ion exchange membrane is a Nafion resin membrane.

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